The correct option is B I, II and III
Differentiated embryonic layers are called ectoderm, mesoderm and endoderm. Mesoglea is the undifferentiated layer present in between the ectoderm and endoderm in sponges. Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals, e.g. coelenterates. Those animals in which the developing embryo has a third germinal layer, mesoderm, in between the ectoderm and endoderm, are called triploblastic animals e.g. platyhelminthes.